Unit 3 Flashcards
Halogens
What do Halogens form when they react with metals?
Salts
Can all halogens exist as diatomic molecules?
Yes they can covalently bond with each other
Are halogens metals?
No, so they cant conduct electricity
Are halogens good oxidising agents or reducing agents
Oxidising agents, Remove electrons form other species have large electron affinity
What happens to the melting/B points as you go down the halogen group?
They increase due to increased mass. More van der waals forces
What property do bromine and iodine have?
They are both volatile ( low boiling point, vaporize easily). All halogens are volatile its just bromine and iodine are solids, the rest are gasses naturally
Iodine goes through a process of sublimation, what does this mean?
When heated it goes straight from a solid to a gas
Why does reactivity decrease down the halogen group?
Because the further down you go means more energy levels (shells) which means it is harder to attract another electron
What is a displacement reaction?
When an element replaces another in the reaction if it is more reactive. So a metal can replace another metal in a metal oxide if it is more reactive and make its own oxide
What does fluorine do to water?
Oxidises it so that it forms oxygen and ozone
What do chlorine and bromine do to water?
They make it an acidic solution
What does iodine do in water?
It is insoluble, but can be dissolved if there are other iodide ions
How do all of the halogens react with hydrogen?
They form covalent bonds.
Fluorine will explode with H
Chlorine will produce chloride gas if there is a flame
bromine will give hydrogen bromide gas
Iodine will only partially combine. an equilibrium is set up
Why does HF have a really high boiling point?
There’s H-bonding
Which halogens are strong acids and why?
All except HF are strong acids as they easily donate a proton.
Why is HF a weak acid?
Ions formed from dissociating the proton (h30+ and F-) are so strongly attracted to each other that they bind, H3O needs to be free in order to be acidic
What is a disproportionation reaction?
One in which an element is both oxidised and reduced at the same time. it produces two products
inter halogens are halogen atoms bonded to a different halogen atom. Are they polar?
Yes due to difference in electronegativity
Electron electron repulsion sequence?
LP-LP> LP-BP>BP-BP
How do you work out the shape of a compound? AX
1) find central atom (A) usually least electronegative
2) Find #of valence electrons in A
3) Count electrons used by other atoms to form bonds
4) is positive ion -1. If negative ion +1
5) add numbers found from steps 2 3 and 4 divide by 2
6) if molecule has double bonds subtract 1
look at the table
What is a cation?
Positively charged ion
What are the halogen oxides good at?
Oxidising
How are oxoacids of halogens formed?
Reacting halogens with their oxides and water. The number of oxygens added the stronger the acid.
Why would acidity decrease along with electronegativity?
As the more electronegative an element the better it is at pulling electrons towards itself making it easier for H+ to be donated. (the more O’s in a oxoacid the more electronegative)
Hydrogen oxidation number?
+1 . if bonded to a metal -1
Oxygen oxidation number?
-2
Fluorine oxidation number?
-1
What is a redox potential?
The tendency of species to be reduced against an electrode with potential value of 0. Reagent with the highest redox potential will be oxidising
What are pseudo halogens and halides?
they mimic the chemistry of halogens and halides
What noble gas was used in lights and could emit a blue glow?
Xenon
What state at the halogens in?
First two are gasses bromine is a liquid the rest are solids
